Real time manufacturing of softening polymers

ABSTRACT

Embodiments of the invention is directed to a manufacturing process to mold and cast custom softening polymers into complex shaped devices, said process comprising the steps of: creating a 3D mold or shell; injecting the shell with a polymer or pre-polymer; cooling or curing the polymer in a short period of time; and forming a device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 61/815,603 filed Apr. 24, 2013, andU.S. Provisional Patent Application No. 61/815,607 filed Apr. 24, 2013which are incorporated herein by reference in its entirety as if fullyset forth herein.

FIELD OF THE INVENTION

Embodiments of the claimed invention are directed to a method forbuilding custom products out of softening polymers.

BACKGROUND OF THE INVENTION

3D printing or additive manufacturing is a process of making athree-dimensional solid object of virtually any shape from a digitalmodel. 3D printing is achieved using an additive process, wheresuccessive layers of material are laid down in different shapes. 3Dprinting is also considered distinct from traditional machiningtechniques, which mostly rely on the removal of material by methods suchas cutting or drilling (subtractive processes).

A 3D printer is a limited type of industrial robot that is capable ofcarrying out an additive process under computer control.

The 3D printing technology is used for both prototyping and distributedmanufacturing with applications in architecture, construction,industrial design, automotive, aerospace, military, engineering, dentaland medical industries, biotech (human tissue replacement), fashion,footwear, jewelry, eyewear, education, geographic information systems,food, and many other fields.

In light of the multiple uses that 3D printing lends itself to, it wouldbe beneficial to use some of the advantages of this technique to buildcustom product using a variety of materials.

SUMMARY OF THE INVENTION

An embodiment of the invention is directed to a manufacturing process tomold and cast custom softening polymers into complex shaped devices,said process comprising the steps of: creating a 3D mold or shell;injecting the shell with a polymer or pre-polymer; cooling or curing thepolymer in a short period of time; and forming a device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of different manufacturing options for creatinga custom softening earphone in accordance with embodiments of theinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An exemplary embodiment of the invention is directed to a manufacturingprocess to mold and cast custom softening polymers into complex shapeddevices, said process comprising the steps of: creating a 3D mold orshell; injecting the shell with a polymer; curing the polymer in a shortperiod of time; and forming a device.

An embodiment of the claimed invention is directed to a method forrapidly building custom products out of softening polymers. Thistechnology uses a combination of scanning and/or 3D printing along withmaterials design technologies. Most softening polymers, such as shapememory polymers described in the literature or materials, suffer frommajor limitations that preclude their use in such a real-timemanufacturing environment. Some limitations include high cure stresses,long polymerization times, improper viscosity of the monomer solutions,the inability of some systems to cure in aerobic environments and eventoxicity of monomers. Softening materials, materials that undergo alarge change in modulus between two variable use temperatures, roomtemperature and body temperature, and especially polymers that soften tomoduli below Shore A 50, have not to our knowledge been successfullyused in a real-time manufacturing paradigm that combines scanning and 3Dprinting. To our knowledge these have not been used as thermoplasticsfor fused deposition printing, or as mixtures of mutually misciblemonomers and additives for curing during stereolithography, reactioninjection molding or real-time casting into complex 3D shells.

A further embodiment of the claimed invention is directed to a methodfor direct stereolithography of softening polymer systems, such thatmaterials can be molded directly in a 3D environment based on a complex3D CAD model. In the past, materials compatible with this paradigm havetraditionally been highly multi-functional materials such as the epoxySU-8 which can be rapidly spot cured with a laser in specific spatialconstructions. A manufacturing process is described herein that is ableto use a material that changes in modulus by at least 2× between roomtemperature and body temperature. We describe a manufacturing paradigmfor materials in which this modulus change occurs to hardness belowShore A 50, below Shore A 30, below Shore A 20 and below Shore A 10. Inone embodiment the materials' modulus changes by more than 100× betweenroom temperature and body temperature. Furthermore, afterpolymerization, the material can be viscoelastic at both roomtemperature and body temperature leading to interesting processingmodifications to deal with time-dependent polymer mechanics.

Another embodiment of the claimed invention is directed to a method thatallows for the printing of a sacrificial polymer shell which is filled(through injection, casting, or some other means) with a custom blend ofmutually miscible monomers which are subsequently polymerized optionallyaround a prefabricated component, such as the custom electronics of anearphone attached to a specially designed tube used to keep monomer fromthe airway that will ultimately lead from the speaker to the eardrum.This embodiment is set forth in FIGS. 1 and 2. This enablescustomization of part of the device and mass manufacture of devicecomponents that can be identical across devices. This manufacturingparadigm also is possible with materials, which once polymerized,possess a modulus change occurs as a function of temperature to hardnessplateaus below Shore A 50, below Shore A 30, below Shore A 20 and belowShore A 10. In one embodiment the materials' modulus changes by morethan 100× between room temperature and body temperature.

Yet another embodiment of the claimed invention is directed to a thirdmanufacturing paradigm in which we can alternatively or simultaneouslyprint a sacrificial polymer shell layer-by-layer and fill and cure orpartially cure a secondary softening polymer that begins to fill thegrowing shell as the shell is being manufactured. This can also beaccomplished by printing the shell and filling the shell around one ormore prefabricated parts that are fully or partially within the boundarycreated by the shell. We believe this approach can be extremely usefulfor creating large parts or parts from polymers (softening or not)without the UV transparency necessary to cure through thick layers. Inthis way, a surface can be cured one layer at a time where thepenetration depth of the curing radiation (e.g. UV) through the materialis greater than the thickness of the layer. In yet another embodiment ofthe layer-by-layer curing within a custom 3D shell, the layers can beonly partially cured such that reactive groups remain on the surface ofthe partially cured layer and are able to effectively form covalentcrosslinks with the next layer. In this way, a structurally sound,well-formed network can be created across custom parts leading toincreases in materials properties such as ultimate tensile strength andtoughness.

An additional embodiment of the claimed invention is the design of a 3Dprinter or print head configuration that allows for this aforementionedparadigm. The 3D printing will include the ability to print an externalshell (likely through Fused Deposition Modeling), to fill the shell witha mutually miscible mixture of photopolymerizable monomers and necessaryadditives (likely through reaction injection molding or injectioncasting) and the cure the shell layer by layer with a UV source. In moresophisticated versions of this machine it is conceivable that thevarious layers could be printed out of different materials that in turncould bind together within the framework created by the outer shell. Inthis way, laminate structures could be created with very interestinganisotropic properties and excellent interlayer adhesion. Specifically,if the UV cure is only a partial cure, such as can be demonstrated withcertain thiol-ene, thiol-ene/acrylate and thiol-epoxy systems, thesevariable interlayers may approach or exceed the materials properties ofa monolithically cured polymer or copolymer.

In an embodiment of the invention, a custom designed 3D printer is ableto print a thin shell in a custom geometry around prefabricatedcomponents such as an earphone connected to an air tube to exclude themixture of mutually miscible monomers that fill the space inside theshell and outside of the tube and component before the monomers arecured. The monomers are cured by a UV source either on the print headthat can cure the monomers layer by layer as the part is being printed,or after several layers or after the entire shell has been filled. Thiscuring profile is dependent on the size of the part, the penetration ofthe UV radiation, the UV transparency of the shell material and the UVtransparency of the monomers themselves and the UV transparency of thecured polymer inside of the shell.

An exemplary embodiment of the claimed invention is directed to amanufacturing process to mold and cast custom softening polymers intocomplex shapes wherein: a 3D mold or shell is created from CAD file,custom (ear) impression, or custom scan; the shell is injected withrapidly curing polymer; and the polymer is allowed to cure in about 15minutes (or shorter/longer depending on use). In embodiment of theinvention, the material is very soft (e.g. less than 50 shore A) and/orhas softening ability (e.g. ˜20-200% change in modulus from room temp tobody temp).

In a further embodiment, a polymer manufacturing process is providedwherein a 3D CAD created from custom (ear) impression, or custom scan;and a part is directly printed from using FDM, SLA, or inkjet printingtechniques. The material is very soft (e.g. less than 50 shore A) and/orhas softening ability (e.g. >20% change in modulus from room temp tobody temp); 1 cures rapidly (less than 10 minutes) under exposure to UVor heat upon printing; and is capable of being directly printed ontoaudio components.

An alternative embodiment is for the design of custom dental aligners orother personalized dental equipment. In this example, a human mouth isscanned or an impression is made and subsequently scanned. The scan istransferred to a program that trims the scan and creates a shell modelthat represents an allowable boundary of the scan. This shell is then 3Dprinted using stereolithography or fused deposition molding techniques.(In another embodiment, the mold is directly cast around theimpression). The shell is then optionally placed around a bundle ofcustom electronics that includes speakers, microphones, cables, andoptionally a variety of other sensors including but not limited to heartrate monitors, blood pressure monitors, pH monitors, and other analytemonitors. In a more specific such embodiment, a patient's mouth isscanned and a series of molds are made from the existing scan in such away as to guide teeth back to some predetermined position for cosmetic,aesthetic, functional, health or other reasons. The first mold isprinted and a polymer or prepolymer is cooled or cured therein such thatthe resulting device exerts a specific force onto the patients' teethand jaws to guide remodeling. Additional parts are likewise fabricatedsuch that the one-time or several-time molds can be rapidly and cheaplymanufactured. This is very important because the costs incurred to makemetal injection molds using subtractive processes are unduly expensivefor low numbers of uses. In addition, often directly printing devices byadditive means leads to tradeoffs in the choice of polymer or prepolymersystem that may not be conducive for the final application. Forinstance, optical clarity plays a huge role in this dental aligningapplication and being able to decouple the polymer properties from thescanning and printing of the custom mold can be very beneficial. In onesuch embodiment, the mold can be 3D printed from commercially availablemetals, ceramics prepolymers or polymers, and filled with differentprepolymers or polymers which are more likely to be able to hit thedemanding application specifications than 3D printable resins. Forinstance, polymers with greater than about 85% transmission throughabout a 500 micron to 1 mm film with an elongation of break above about50% and yield strength of about 48 MPa and a glassy modulus above about1 GPa can be achieved in many non-3D printed resins. One such prepolymeris a monomer resin of thiols and alkenes which when polymerizedpossesses high optical clarity, low or zero-cure stresses, delayednetwork gelation and excellent mechanical properties. When a materialsuch as this is developed toward a 3D printing resin, additives,reactive diluents, colorants, dyes, and other agents may be necessaryfor printing but not for the application itself. This invention finds aclever way around this quite difficult issue and can present a way toreduce yellowing of the final part.

In a further embodiment of this invention, the final molds can haveshape memory properties, such that instead of requiring many multiplesof molds (up to 40 in some cases), only one or a much smaller number ofdental aligners can be made in the manner described above and utilizethe shape memory effect to gradually or periodically reshape the moldand control the applied forces on the teeth and jaw.

Another embodiment of the invention is for the design of a toy, noveltyitem, bobble head doll, action FIGURE or other likeness. The targetobject to be scanned, photographed or otherwise converted into a 3Dgeometry or superposition of 2D geometries, may be but is not limited toa target person, pet, animal, body part, household item or toy, case forconsumer electronics, sculptures, artwork or other physical orintellectual creative endeavor.

In certain embodiments of the invention, the injection system is builtdirectly into 3D printer (i.e. able to position and automate casting orreaction injection molding); and the material is liquid or gel systemcapable of injection into shell. In certain embodiments, the injectionand/or finishing can also be designed separately from 3D printer.Additionally, finishing can be accomplished through polish, liquidepoxy, etching, micro-milling, cryomilling, solution dipping, coating orsurface functionalization

In some embodiments, the material is optionally formed aroundprefabricated components. In an embodiment for the manufacture of anearphone, a sound tube is connected and automatically positioned at thetarget center to cast around (for earphones). The shell is printeddirectly on to the audio component or the shell is attached to the audiocomponent prior to the injection of the material. The material istypically UV curable or thermally curable and could contain colorants orthermochromic dyes. In certain embodiments, subtractive processing maybe used to create semi-custom styles (e.g. sport fit of earphone thatlets in some sound). Alternately, the incorporation of sensors (e.g.heart rate, O₂, temp) and connection to phone for sports performance orhealth monitoring (another potential embodiment).

FIG. 1 shows a schematic process for the design of a custom earphonewith a softening material. In a first process, the following steps arefollowed:

Data collection:

-   -   Digital scanning of ear canal;    -   Take impression of ear canal, scan impression

Data filtering:

-   -   Trim and filter scanned data    -   Trim and smooth physical ear impression (no scan required)

Mold Production:

-   -   3D print the custom device mold (FDM)    -   3D print the custom device mold (SLA)    -   Cast mold directly from physical impression

Custom Device:

-   -   3D print device directly (no mold production required)    -   Cast the device into mold created by FDM, SLA or from physical        impression

Automation/Integration:

-   -   Software algorithm to recognize changes in geometry of ear canal        to trim the data just outside the ear canal and inside the ear        canal prior to negative draft    -   Software algorithm to produce an outward shell of the data so        that inner surface matches the inner surface of ear canal.    -   Software algorithm to orient and skew the mold impression to        avoid overhangs greater than threshold of print quality required        for FDM printing (commonly, but not limited to, 45 degrees)    -   Software algorithm to produce features for custom devices,        selectable by technician, including, but not limited to, holes        and geometry for audio tubes, electrical components, audio        speakers, and hearing aid components.    -   Custom additive or subtractive manufacturing hardware capable of        producing a mold using an additive manufacturing technique        (including but not limited to FDM and SLA), followed by assembly        of electrical components, injection of curable liquid resin into        the mold and rapid curing of the resin to produce custom-fit        devices (see attached diagram)    -   Custom additive manufacturing hardware capable of directly        producing custom ear-canal devices incorporating other        components including, but not limited to, audio tubes,        electrical components, audio speakers and hearing aid        components.

The claimed invention is directed to a comprehensive, real-timemanufacturing paradigm in which devices are made from softening polymersthat comprises several steps:

-   -   a) Laser scanning, acoustic scanning, thermal scanning, or        otherwise capturing of a 3D image of a part, body part,        component, space, relevant subject matter or specified mold or        impression made to represent said part;    -   b) A software algorithm to trim and shell scanned data;    -   c) A method, such as wireless data transfer, to send the 3D        model to a 3D printer;    -   d) Printing a material shell of an optionally sacrificial        material;    -   e) Optionally positioning the material shell around        prefabricated components, which could include other components        made through this disclosed process, or materials such as but        not limited to custom electronics, stiff structural materials or        encapsulated biological materials;    -   f) Casting a combination of mutually miscible monomers into the        shell that are subsequently fully or partially polymerized in        the custom mold;    -   g) Optionally deforming a partially polymerized device further        and completing the polymerization process to achieve        extraordinary shapes; and    -   h) Performing any necessary post processing steps on the device,        such as custom finishing, polishing, and milling.

A preferred embodiment of the invention is the design of customearphones. In this example, a human ear canal is scanned or animpression is made and subsequently scanned. The electronic scan istransferred to a program that trims the scan and creates a shell modelthat represents an allowable boundary of the scan. This shell is then 3Dprinted using stereolithography or fused deposition molding techniques.In another iteration, a physical shell is cast around the physical earimpression. This shell is then placed around a bundle of customelectronics that includes speakers, microphones, cables and optionally avariety of other sensors including but not limited to heart ratemonitors, blood pressure monitors, pH monitors, and other analytemonitors.

Other embodiments are directed to a custom manufacturing process forcreating a custom earphone for a user in less than 3 hours and morepreferably less than 1 hour, less than 30 minutes, less than 20 minutes,less than 15 minutes, less than 10 minutes, and less than 5 minutes.

A further embodiment is directed to a custom manufacturing process forcreating an earphone with a softening polymer interface that can becompleted in less than 30 minutes.

While particular embodiments of the present disclosure have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the disclosure. It is thereforeintended to cover in the appended claims all such changes andmodifications that are with the scope of this disclosure.

What is claimed is:
 1. A manufacturing process to mold and cast customsoftening polymers or prepolymers into complex shaped devices, saidprocess comprising the steps of: creating a 3D mold or shell; injectingthe shell with a polymer or prepolymer; cooling the polymer melt orcuring the prepolymer in a short period of time; and forming a device.2. The process of claim 1, wherein the shell geometry is generated usinga laser scan, a physical impression, splicing of pictures taken frommultiple angles, image processing and interpolation from a singlepicture or an alternative scanning of the object to be molded.
 3. Theprocess of claim 1, wherein the shell is manufactured by additive meanssuch as fused filament fabrication, stereolithography, digital lightprojection based selective curing, inkjet printing, selective lasersintering or selective deposition lamination.
 4. The process of claim 1,further comprising using a software algorithm to trim and shell scanneddata.
 5. The process of claim 1, further comprising transferring data tosend the 3D model to a 3D printer by wireless or wired means.
 6. Theprocess of claim 1, further comprising printing a material shell of anoptionally sacrificial material.
 7. The process of claim 1, furthercomprising positioning the material shell around prefabricatedcomponents such as but not limited to custom electronics, stiffstructural materials or encapsulated biological materials.
 8. Theprocess of claim 1, wherein the polymer comprises a combination ofmutually miscible monomers that are subsequently fully or partiallypolymerized in the shell.
 9. The process of claim 1, wherein the polymeror prepolymer is cured by a UV source or other optical energy sources.10. The process of claim 1, further comprising optionally deforming apartially polymerized device further and completing the polymerizationprocess to achieve extraordinary shapes.
 11. The process of claim 1,further comprising performing post processing steps on the device, suchas custom finishing, polishing, and milling.
 12. The process of claim 1,wherein the process is used to manufacture earplugs, earphones,bluetooth devices, hearing aids and other personalized audio equipment.13. The process of claim 1, wherein the process is used to manufacturedental aligners or other personalized dental equipment or devices. 14.The process of claim 1, wherein the process is used to manufactureend-use products with the requisite properties such as but not limitedto mechanical, thermal, electrical, piezoelectric, optical, structural,biological, or chemical to directly be used in manufacturingenvironments.
 15. The process of claim 1, wherein the process is used tomanufacture biomedical devices including but not limited to syringes,catheters, valves, stents, suture anchors, needles, bandages, arterialclamps, punctual plugs, septal plugs, synthetic bones, syntheticcartilage, synthetic tendons, custom prosthetics, tissue phantoms,scaffolds, or cellular scaffolds of specific shapes.
 16. The process ofclaim 1, wherein the injecting process used is injection molding, blowmolding, vacuum assisted resin transfer molding, reactive injectionmolding, foaming or casting.
 17. The process of claim 11, wherein thepost-finishing or polishing is performed by laser ablation.
 18. Theprocess of claim 12, wherein the audio equipment is coated with one ormore compounds that resist bacteria growth, boost immune system, andenhance compatibility of the audio equipment with human organs.
 19. Theprocess of claim 13, wherein the dental equipment is coated with one ormore compounds that resist bacterial growth, boost immune system andenhance compatibility of the dental equipment with human organs.
 20. Theprocess of claim 15, wherein the biomedical devices are coated with oneor more compounds that resist bacterial growth, boost immune system andenhance compatibility of the biomedical devices with human organs.